Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
  • H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/016—Flame-proofing or flame-retarding additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/14—Peroxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/006—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to block copolymers containing at least one sequence of polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/04—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to rubbers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/28—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances natural or synthetic rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2201/00—Properties
  • C08L2201/02—Flame or fire retardant/resistant
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/16—Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers

Definitions

• the present invention relates to a process of producing fire resistant thermoplastic based materials, to the polymer compositions thus obtained and to the products using said compositions .
• the invention relates to halogen-free thermoplastic materials that, filled with a high level of inorganic compounds, grafted in bulk with compatibilizing substances and dinamically "cured” with free radical generator catalysts, are both fire resistant and provided with surprisingly high thermomechanical properties.
• Halogen-free thermoplastic materials have a broad and useful range of mechanical properties.
• polyolefins are a chemically homogeneous class of polymers with a wide spectrum of properties and a low level of environmental impact, so their use is growing with an impressive rate and new materials, obtained from new catalitic systems, came into the market offering new applications .
• thermoset materials that contain mainly carbon and hydrogen, can burn and propagate the flame very easily and there has been a constant search for a way of removing this characteristic without compromising their mechanical properties and without transforming them in thermoset materials.
• a first, known, solution is to use inorganic compounds, i.e. metal hydroxides (e.g. Mg and Al hydroxides), oxides and/or inorganic salts, having endothermical decomposition and releasing nonflammable gas (like water or carbon dioxide) , and/or creating a protective shield when heated, as fillers in plastics or elastomers to impart flame retarding properties to said materials.
• inorganic compounds i.e. metal hydroxides (e.g. Mg and Al hydroxides), oxides and/or inorganic salts, having endothermical decomposition and releasing nonflammable gas (like water or carbon dioxide) , and/or creating a protective shield when heated, as fillers in plastics or elastomers to impart flame retarding properties to said materials.
• the flame retarding action of these inorganic compounds is based on physical reasons. Their endothermic thermal decomposition process subtracts heat to the burning bulk, reducing the release of flammable pyrolytic gases, and further diluting it with non flammable gas released by the inorganic compounds. In addition some of them can create a protective layer that acts as a shield against the flame propagation.
• the main drawback of these inorganic fillers is that their effectiveness is pretty low and a high amount of filler is required to impart the polymer effective fire retarding properties (particulary with resins, like polyolefins, that can burn completely) . In fact, the required amount of filler is so high that the mechanical properties of the final material are dramatically jeopardized.
• the aim of the present invention is to improve the mechanical properties of halogen-free fire resistant thermoplastic materials in which the fire resistance is given by an inorganic filler, by means of a chemical modification of the polymeric matrix during the blend with the filler, and to substantially maintain the thermoplastic characteristics of the starting materials in the final composition.
• the invention relates to a reactive process to prepare halogen- free thermoplastic compositions having fire resistance characteristics, according to claim 1.
• the inorganic filler is selected from Al(OH) 3 , g(OH) 2 , CaC0 3 , boric acid, borates, CaO, silica and mixtures thereof;
• the radical generating agent is a peroxide and the compatibilizing agent is selected from maleic and fumaric acids, maleic and fumaric anhydrides and mixtures thereof.
• This invention also concerns halogen-free, fire resistant thermoplastic compositions as obtainable according to the claimed process, wherein compatibilizing agents are grafted over all the bulk of said thermoplastic material.
• the final composition is thermoplastic and is partially crosslinked.
• the invention also relates to electric cables provided with a layer made with a fire resistant thermoplastic material according to the invention. Preferably, such layer is a shield.
• the invention also relates to the use of a composition as above disclosed for the production of electric appliances and their parts, such as boxes, pipes, etc.
• the invention provides several advantageous features.
• the invention process results in a final composition that is thermoplastic, i.e. it is further processable and recyclable. There thus is no need to give the product its final shape before curing it by heating the mixture and activating the peroxides; in fact a preferred shape for the invention composition is as pellets.
• the invention compositions have surprisingly good properties, namely higher values of mechanical modulus, stress strain and elongation at break, impact behaviour, abrasion resistance, compression set and softening or distortion temperature, with respect to the properties of corresponding materials made according to known techniques.
• thermoplastic material useful for carrying out the process are selected from alpha- defines homo and co-polymers such as ethylene, propylene, ethylene/propylene, propylene copolymers containing one or more alpha olefins with 2-10 carbon atoms (e.g.
• SBR styrol/butadiene rubbers
• the starting thermoplastic material must contain both crosslinkable and non-crosslinkable compounds.
• the amount of thermoplastic material is usually about 5-70 wt.%, in any case it is such as to bring to 100 the composition.
• the inorganic fillers imparting fire resistance are those inorganic fillers that endotermically decompose with release of non-flammable gas and inert ashes. Examples of these fillers are aluminiun trihydroxide, magnesium hydroxide, huntite [3MgC ⁇ 3xCaC0 3 ] or hydromagnesite [Mg 5 (C0 3 ) 4 (OH) 2 x 4H 2 0], boric acid.
• Other suitable fillers are those that can vetrify like borate or hydrate borate, sodium bicarbonate, calcium oxide and silica.
• the fillers can be mixed together or diluted with inert materials like silica, or materials that decompose at higher temperatures than the polymer decomposition temperature, like calcium carbonate. Their total amount is within the range of 30- 80 wt.%, typically from 40% to 75% by weight of the final blend.
• the co patibilizers are molecules with chemical affinity to the filler, and able to graft, with a chemical bond, the macromolecular backbone by means of a free radical catalyzed reaction.
• these compatibilizers are unsaturated organic acids or esters, like acrylic, methacrylic, fumaric, maleic, citraconic or itaconic acid and esters, used in a concentration ranging between 0,005 and 10% by weight of the blend.
• compatibilizers are maleic and fumaric acids, maleic anhydride and mixtures thereof.
• Another class of useful compatibilizers are the maleinized polybutadienes or vinyl- methoxysilanes that can graft the macromolecular backbone accelerating and or promoting the crosslinking reaction, used in concentration till 15% of the total blend.
• the preferred amount of compatibilizers is within the range of 0.01-15 wt.%.
• the free radicals generator agentss are preferably organic peroxides like dicumil peroxide, 2, 5-di (terbutylperoxi) -2, 5- dimethylhexane, or other molecules with a strained bond that omolitically breaks upon temperature increase, like 2,3- dimethyl-2, 3-diphenyl-butane.
• radical generator agents start radical chain reactions that both graft the compatibilizer molecule onto the macromolecules but also "cure" the polymer by crosslinking.
• radical generating agents are provided in an amount of 0.01-2.0 wt.% of active material.
• thermoplastic composition that is fire resistant, free from halogens and really thermoplastic (i.e.
• a blend comprising: a halogen- free thermoplastic material containing both crosslinkable and non-crosslinkable compounds, a fire resistant inorganic filler, a compatibilizing agent for said inorganic filler, and a radical generating agent, and to dinamically cure said blend to obtain a partially crosslinked thermoplastic composition.
• Blends "Dinamically curing" the above blend or mixture means that the blend is melted and kneaded at a temperature above the decomposition temperature of said radical generating agent in order to start and carry out the reticulation of the macromolecules, i.e. the crosslinking, or the degradation of the macromolecules, according to their nature.
• the action of the radical generating agents occurs in the presence of the filler and of the compatibilizer to obtain the required grafting
• the macromolecular structure of the thermoplastic material is modified in a way that depends from its initial structure and composition: with polymers having unsaturated carbon-carbon bonds like ethylene/propylene/diene rubber or styrole/butadiene rubber, or having more than 50% (moles) of ethylenic units in the backbone like polyethylene, ethylene/1-octene (or 1-hexene) copolymers, ethylene/propylene rubber, ethylene/vinylacetate, hydrogenated styrole/butadiene rubber the main result of the radical chain reactions is a macromolecular crosslinking.
• the main radical reaction is a chain scission or degradation to give shorter chains.
• This structural change control is a crucial point to improve the material characteristics that can be customized balancing the degradation and the crosslinking by accurate polymer and additives choice.
• polymers like polypropylene that is degradated by radical generators, without any crosslinking reaction, are frequently employed.
• the control of this degradation and some degree of crosslinking is possible by employing polymers rich in double bonds such as polybutadienes, polyalkenylenes, plyenes and EP(D)M rubbers that graft and join the macromolecules by free radical catalyzed reactions.
• a curable rubber is frequently employed but the complete crosslinking that should transform the polymer in a termoset material is avoided by using some amount of polypropylene or other non-crosslinkable compound.
• the non-crosslinkable, degradable, compound substantially acts as a continuous phase in which the cured (or crosslinked) phase is dispersed.
• the formulation of the composition i.e. the amounts of degradable polymers, curable polymers, peroxide and polymers rich in double bonds, is balanced according to the mechanical characteristic that are required for the final product. If elastomeric properties are required, a greater amount of crosslinkable compounds will be present in the initial thermoplastic material; if a rigid final product is required, the amount of degradable, non-crosslinkable (i.e. uncurable) compound will be greater than the amount of curable (crosslinkable) compound.
• the invention process provides to carry out the mixing, melting, kneading, compatibilizing and curing/degrading of the blend components substantially in one step.
• the inorganic filler is usually added immediately after the reaction is started on the rest of the mixture, as disclosed by the following examples.
• a preferred apparatus to carry out the process is an extruder, most preferably co-rotating twin screws extruders with a high dispersing and homogeneization capacity, good temperature control and high ratio L/D, where L is the barrel length and D is the barrel diameter.
• examples 1, 5 and 6 are referring to state of the art processes.
• no peroxide or compatibilizing agent was used; in 5 and 6 the compatibilizing agent (comp 1 ) was previously grafted on a polymer matrix (polypropylene) and subsequently added to the invention blend, the poor results are self evident, also in ex.6 where a high amount of comp 1 was added.
• Example 2 shows a comparative example in which peroxide only was used.
• Example 3 repeats the formulation of example 2, with the addition of maleic anhydride: the value of tension at break increased from 16 to 20 MPa.
• comp is a compatibilizing agent "POLYBOND 3150” ® by Uniroyal Chemical
• examples 3-10 refer to rigid compositions and show the surprising results of invention composition 11 with respect to comparative examples 9 and 10.
• the added legenda references for table 2 are: 8) ASTM 1238 (230°C, 2.16)
• EPDM Dutral Ter 4038 by Enichem Elastomeri

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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 1997
  • 1997-11-21 AU AU51349/98A patent/AU5134998A/en not_active Abandoned
  • 1997-11-21 EP EP97946051A patent/EP1034219A1/de not_active Withdrawn
  • 1997-11-21 WO PCT/IT1997/000291 patent/WO1999027015A1/en not_active Application Discontinuation

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